| Why this ELECTRICITY? By Eng. Navodana Kankanamge |
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Consume lavishly and regret when billed OR consume efficiently and enjoy life’s comforts affordably.
Although electricity tariff has been modified recently the generation cost of electricity is still higher than its selling price in Sri Lanka. The only way to reduce the electricity bill is by improving the efficiency and the effectiveness of electricity usage. It is obvious that Electrical Engineers in the country most likely participate in discussions on this subject. Following facts may be of help to anybody interested in reducing the electricity consumption without losing the comforts of life made possible by it.
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| Refrigerators |
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| Refrigerators play an essential role in modern life. They provide steady cooling and among other things allow us to easily preserve food. It is estimated that almost 50% of the domestic energy consumption is due to the use of a refrigerator. There are around 4 million domestic consumers in the country and it is estimated that more than 60% among them are using a refrigerator. Energy consumption of a refrigerator is affected by the following factors. |
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When choosing a location with the required clearances for placing the refrigerator, you need to consider the temperature in the location. If the temperature is too high, the compressor of the refrigerator will run more often and use more energy. Air circulation helps keep the temperature down around the refrigerator. Don’t place the refrigerator right up against the wall; the warm air from the refrigerator’s condenser coil has nowhere to escape. Normally the refrigerator maintains an interior temperature at 4C and 18C in the freezer for safe food storage. If the distance from the wall is not adequate, the warm air trapped around the unit will make it run more often to maintain the correct internal temperature.
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Compressor operating time increases with the frequency and duration of door opening since the cold air inside escapes out from the bottom and isreplaced by hot air from outside. If door opening frequency is difficult to control, plastic air curtain can be used to trap cold air successfully when door opens. It is very cheaper and simple improvement to reduce the energy consumption. Food in the freezer section should be transferred to the normal refrigeration section about half an hour before use. This will help to reduce the compressor load. If cool air leaks through the sides of the door, the magnetic rubber beading needs to cleaned or replaced. When food items are left uncovered inside the refrigerator, it will release its moisture into the air and the compressor of the refrigerator has to work twice as hard to remove it. Using empty bottles, containers, or even store bought water jugs can help keep space full and it helps keep things cold.
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| Electric Cookers |
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An induction cooker transfers electrical energy by induction from a coil of wire into a metal pot. It is more energy-efficient than other electric cookers. It allows excellent temperature control as well. Water heaters, kettles, hot plates and rice cookers could can be easily replaced with a programmable induction cooker.
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An induction coil mounted inside the cooker passes a large alternating current, causing a strong alternating magnetic flux. The changing magnetic field flux induces an electrical current (eddy current) in the bottom plate of pot, which is a thicker construction than a normal vessel. The eddy current, flowing through the electrical resistance inside the pot, produces heat, just where it is needed, when it is needed and most importantly in the required quantity.
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| Automation possibilities |
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Electrical equipment are frequently forgotten to be switched offafter use when the service is no longer needed. Outdoor lights left on during day times, fans and lights working even without anybody inside the room are common examples of such wastage. Modern technology could easily be utilized to automate these appliances. Programmable timer relays, proximity sensors along with relay modules, water level sensors with programmable relay modules are freely available and even easily purchased online and shipped to any place you wish from web sites like eBay. You may try them yourself as a trial since they are not much expensive.
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| Lighting |
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| Lumens (lm) |
Incandescent (W) |
CFL (W) |
LED (W) |
| 2600 |
150 |
32 |
25 |
| 1600 |
100 |
23 |
16 |
| 1100 |
75 |
18 |
13 |
| 800 |
60 |
13 |
8 |
| 450 |
40 |
9 |
6 |
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| Life Span (hr) |
1,200 |
8,000 |
30,000 |
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It is clear that incandescent lamps are highly in-efficient. Light Emitting Diode (LED) the latest technology for the lighting and LED bulbs are even more energy-efficient and more durable than Compact Fluorescent Light (CFL) bulbs. Even though LED requires less wattage than CFL for the same amount of light, using CFL bulbs are still worth considering for its lower capital investment and the quality of the light. For a comprehensive study see the data given in the Table.
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For sensitive lighting requirement such as industrial applications, T5 fluorescent tube lamps driven by electronic ballasts are best suited. T5 lamps are both electrically and physically incompatible with T8 and T12 fluorescent lamps. T5 fluorescent is the first linear lamp type to be served only by electronic ballasts. It is smaller than T8 and T12 lamps, and efficacy is very close to LED lamps. It is interesting to note that the number following the letter T is in fact the diameter of the tube, expressed in multiples of 1/8th of an inch. Hence a T5 will have a tube with a diameter of 5/8 inches.
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| Televisions |
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LED television is more energy efficient, provides a brighter display and provides better contrast than a LCD television. Contrary to popular belief, LED TVs are again LCD TVs which uses uses light-emitting diodes for backlighting as opposed to CCFLs used in televisions usually referred to as LCD TVs. It has thinner panel, and lesser heat dissipation.
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| Water pumps |
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Submersible type pumps are more efficient than suction type pumps. Motor specification varies with the application. Head, pumping capacity, pumping diameter and output power are key factors that need to be examined. Two water level sensors along with programmable relay switch could be used to automate the motor to avoid tank overflows and tank becoming empty.
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| Electricity shall be used only for essential requirements during system peak |
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It’s obvious that generation cost of electricity is higher during the system peak around 6.30pm to 9.30pm since thermal power plants are dispatched to meet the demand. More electricity consumption during peak results in more generation cost for the utility. The apparent disconnection between time
of use and tariff paid by the domestic user conceals the true picture. More electricity used by the domestic user during the peak hour is a definite positive contributor to tariff increases. Finally it is reflected on the electricity tariffs paid by all users.
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